The advent of global terrorism has captured world attention for the detection, location and discrimination of mines and Improvised Explosive Devices (IEDs). Detecting these threats is very challenging, and thus far research has not revealed one phenomenon or “silver bullet” which can reliably provide the needed capability against these threats. Instead, the best approach currently appears to be a melding or integration of several technologies in order to better the performance over any one technology.
Metal detectors, more technically referred to as Electromagnetic Induction (EI) sensors can detect the metal in mines and IEDs. It is very effective against some mines and less so against newer “low metal” mines. Ground Penetrating Radar (GPR) can provide good capability to indicate the presence of an object under ground but may lack good discrimination performance against rocks and similar underground artifacts. If one were to combine EI sensing with GPR sensing the two would complement each other with a net overall improvement in capability against many mines and IEDs.
However, there is a problem with using both these technologies together. Invariably one does not want a multiplicity of sensor heads for both practical reasons plus co-registration reasons. Further, if such detectors are to be borne by soldiers, they must be simple and light weight which suggests that that the sensor must be one unit even if it uses multiple technologies. This suggests that the sensor heads need to be melded into one light weight holistic unit, and not a multiplicity of different separate units.
A problem presents when trying to combining the sensor head of an EI sensor with that of a GPR sensor in that GPR requires metallic antennas to operate, and at the same time, any such metallic antenna, if closely integrated with an EI sensor will necessarily place the metallic antenna in close proximity to the EI sensor coil. This will tend to saturate the EI sensor and at least degrade its sensitivity and dynamic range and possibly make it ineffective. The reason for this is obvious in that an EI sensor is designed to detect metal and if the GPR antenna is made of metal and placed close to the EI coil, it almost cannot help but detect the GPR antenna metal. The resulting degradation in EI performance takes away from the otherwise highly desirable synergism between these two sensors, thereby negating a significant amount of the motivation for combining them. The objective of this invention is to remove that limitation and to enable the EI sensor to realize its full performance capability in the proximate presence of a GPR antenna.